This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular to, a transition member for a gravel packing apparatus that maintains fluid slurry velocity therethrough.
Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbons through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulates. For example, the particulates cause abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulates may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a workstring to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the workstring and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulates carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.
It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.
Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge. It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation. In addition, it has been found, that it is difficult and time consuming to make all of the necessary transition sections between the numerous joints of shunt tubes required for typical production intervals. Moreover, it has been found that the velocity of the fluid slurry may decrease below the settling velocity of the fluid slurry in these transition sections such that the gravel drops out of the fluid slurry and clogs the transition section preventing further flow therethrough.
Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation. Further, a need has arisen for such an apparatus that is not difficult or time consuming to assemble. Moreover, a need has arisen for such an apparatus that maintains sufficient velocity of the fluid slurry in transition sections.
The present invention disclosed herein comprises an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. The apparatus and method of the present invention not only allow for the delivery of the gravel packing fluid slurry but also maintain sufficient velocity of the fluid slurry in transition members that couple together two slurry delivery devices, such as gravel packing apparatuses.
Each of the transition members comprises a first end that is coupled to one slurry delivery device and a second end that is coupled to another slurry delivery device. Each of the slurry delivery devices has a slurry passageway with a cross sectional area that determines the volumetric capacity of slurry that may be pumped therethrough. The transition member includes a transition passageway that provides fluid communication between the slurry passageways of the two slurry delivery devices coupled to the transition member.
In one embodiment of the transition members, at least a portion of the transition passageway has a cross sectional area that approximates the cross sectional area of the slurry passageways of the slurry delivery devices. This matching of areas maintains the fluid slurry velocity when the fluid slurry travels through the transition member. In this embodiment, the transition passageway may comprise an annular area that may have an annular throat, wherein the annular throat has a cross sectional area that approximates the cross sectional area of the slurry passageways. Alternatively, the transition passageway may comprise a plurality of longitudinal fluid passageways or a spiral passageway.
In another embodiment of the transition members, the transition passageway may comprise inner and outer surfaces that define an annular passageway therebetween wherein at least one of the inner and outer surfaces is contoured such that the distance between the inner and outer surfaces varies along the length of the annular passageway, thereby maintaining fluid slurry velocity when the fluid slurry travels through the transition member. Whether the contoured surface is the inner surface, the outer surface or both the inner and the outer surfaces are contoured, the contoured surface may be an arc like surface, a pyramid shaped surface, a pyramid shaped surface with a plateau or other suitably shaped surface that maintains the fluid slurry velocity when the fluid slurry travels through the transition member. Regardless of the shaped of the contoured surface, the annular passageway may comprise an annular throat, wherein the annular throat has a cross sectional area that approximates the cross sectional area of the slurry passageways of the slurry delivery devices.
In another aspect, the present invention is directed to a method for maintaining fluid slurry velocity in a transition member between two slurry delivery devices, such as gravel packing apparatuses. The method comprises the steps of coupling a transition member between the two slurry delivery devices which establishes fluid communication from a slurry passageway of one slurry delivery device to a slurry passageway of the other slurry delivery device through a transition passageway of the transition member. Additionally, the method includes disposing the transition member and the slurry delivery devices downhole, pumping a fluid slurry into the slurry passageway of one of the slurry delivery devices, through the transition passageway of the transition member and into the slurry passageway of the other the slurry delivery devices, and maintaining the fluid slurry velocity in the transition member. This is achieved, for example, by making the cross sectional area of at least a portion of the transition passageway approximately the same as the cross sectional area of the slurry passageways, contouring at least one of the inner and outer surfaces of an annular passageway such that the distance between the inner and outer surfaces varies along the length of the annular passageway or both.